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As scorching heat grips large swaths of the Earth, a lot of people are trying to put the extreme temperatures into context and asking: When was it ever this hot before?

Globally, 2023 has seen some of the hottest days in modern measurements, but what about farther back, before weather stations and satellites?

Some news outlets have reported that daily temperatures hit a 100,000-year high.

As a paleoclimate scientist who studies temperatures of the past, I see where this claim comes from, but I cringe at the inexact headlines. While this claim may well be correct, there are no detailed temperature records extending back 100,000 years, so we don’t know for sure.

Here’s what we can confidently say about when Earth was last this hot.

This is a new climate state

Scientists concluded a few years ago that Earth had entered a new climate state not seen in more than 100,000 years. As fellow climate scientist Nick McKay and I recently discussed in a scientific journal article, that conclusion was part of a climate assessment report published by the Intergovernmental Panel on Climate Change (IPCC) in 2021.

Earth was already more than 1 degree Celsius (1.8 Fahrenheit) warmer than preindustrial times, and the levels of greenhouse gases in the atmosphere were high enough to assure temperatures would stay elevated for a long time.

Earth’s average temperature has exceeded 1 degree Celsius (1.8 F) above the preindustrial baseline. This new climate state will very likely persist for centuries as the warmest period in more than 100,000 years. The chart shows different reconstructions of temperature over time, with measured temperatures since 1850 and a projection to 2300 based on an intermediate emissions scenario. D.S. Kaufman and N.P. McKay, 2022, and published datasets, Author provided

Even under the most optimistic scenarios of the future – in which humans stop burning fossil fuels and reduce other greenhouse gas emissions – average global temperature will very likely remain at least 1 C above preindustrial temperatures, and possibly much higher, for multiple centuries.

This new climate state, characterized by a multi-century global warming level of 1 C and higher, can be reliably compared with temperature reconstructions from the very distant past.

How we estimate past temperature

To reconstruct temperatures from times before thermometers, paleoclimate scientists rely on information stored in a variety of natural archives.

The most widespread archive going back many thousands of years is at the bottom of lakes and oceans, where an assortment of biological, chemical and physical evidence offers clues to the past. These materials build up continuously over time and can be analyzed by extracting a sediment core from the lake bed or ocean floor.

These sediment-based records are rich sources of information that have enabled paleoclimate scientists to reconstruct past global temperatures, but they have important limitations.

For one, bottom currents and burrowing organisms can mix the sediment, blurring any short-term temperature spikes. For another, the timeline for each record is not known precisely, so when multiple records are averaged together to estimate past global temperature, fine-scale fluctuations can be canceled out.

Because of this, paleoclimate scientists are reluctant to compare the long-term record of past temperature with short-term extremes.

Looking back tens of thousands of years

Earth’s average global temperature has fluctuated between glacial and interglacial conditions in cycles lasting around 100,000 years, driven largely by slow and predictable changes in Earth’s orbit with attendant changes in greenhouse gas concentrations in the atmosphere. We are currently in an interglacial period that began around 12,000 years ago as ice sheets retreated and greenhouse gases rose.

Looking at that 12,000-year interglacial period, global temperature averaged over multiple centuries might have peaked roughly around 6,000 years ago, but probably did not exceed the 1 C global warming level at that point, according to the IPCC report. Another study found that global average temperatures continued to increase across the interglacial period. This is a topic of active research.

That means we have to look farther back to find a time that might have been as warm as today.

The last glacial episode lasted nearly 100,000 years. There is no evidence that long-term global temperatures reached the preindustrial baseline anytime during that period.

If we look even farther back, to the previous interglacial period, which peaked around 125,000 years ago, we do find evidence of warmer temperatures. The evidence suggests the long-term average temperature was probably no more than 1.5 C (2.7 F) above preindustrial levels – not much more than the current global warming level.

Now what?

Without rapid and sustained reductions in greenhouse gas emissions, the Earth is currently on course to reach temperatures of roughly 3 C (5.4 F) above preindustrial levels by the end of the century, and possibly quite a bit higher.

At that point, we would need to look back millions of years to find a climate state with temperatures as hot. That would take us back to the previous geologic epoch, the Pliocene, when the Earth’s climate was a distant relative of the one that sustained the rise of agriculture and civilization.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Watch this TED-Ed video to learn more about how weather has been affected by climate change: 

ABOUT THE AUTHOR

Darrell Kaufman is a Regents’ Professor in the School of Earth and Sustainability at Northern Arizona University. He has been researching the Quaternary geology and paleoclimatology of Alaska for over 30 years. He has a special interest in geochronology and in coordinating large collaborative science synthesis projects. His research group studies geologic records of environmental changes to understand how the Earth system responds to natural and anthropogenic forcings on millennial time scales. It focuses on lake sediments from Alaska, geochronology, and proxy climate syntheses.

Georgina Smith / CIAT

November’s UN climate conference, COP26, turned a spotlight on the climate crisis.

But in order to better understand the policies and impacts of global warming, it’s useful to understand the science behind it.

I’m an atmospheric scientist who has worked on global climate science and assessments for most of my career.

Here are six things you should know, in charts:

Chart 1: Since 1960, CO2 levels have been steadily climbing

The primary focus of the negotiations at COP26 has been on carbon dioxide, a greenhouse gas that is released when fossil fuels — coal, oil and natural gas — are burned, as well as by forest fires, land-use changes and natural sources.

The Industrial Revolution of the late 1800s started an enormous increase in the burning of fossil fuels. It powered homes, industries and opened up the planet to travel. That same century, scientists identified carbon dioxide’s potential to increase global temperatures, which at the time was considered a possible benefit to the planet. Systematic measurements started in the mid-1900s and have shown a steady increase in carbon dioxide, with the majority of it directly traceable to the combustion of fossil fuels.

NOAA Global Monitoring Lab

Chart 2: CO2 stays in the atmosphere for hundreds of years

Once in the atmosphere, carbon dioxide tends to stay there for a very long time. A portion of the carbon dioxide released through human activities is taken up by plants, and some is absorbed directly into the ocean, but roughly half of all carbon dioxide emitted by human activities today stays in the atmosphere — and it likely will remain there for hundreds of years, influencing the climate globally.

During the first year of the pandemic in 2020, when fewer people were driving and some industries briefly stopped, carbon dioxide emissions from fuels fell by roughly 6 percent. But it didn’t stop the rise in the concentration of carbon dioxide because the amount released into the atmosphere by human activities far exceeded what nature could absorb.

If civilization stopped its carbon dioxide-emitting activities today, it would still take many hundreds of years for the concentration of carbon dioxide in the atmosphere to fall enough naturally to bring the planet’s carbon cycle back into balance because of carbon dioxide’s long life in the atmosphere.

Pieter Tans

Chart 3: When CO2 levels go up, so do global temperatures

Multiple lines of scientific evidence point to the increase in greenhouse emissions over the past century and a half as a driver of long-term climate change around the world. For example:

- Laboratory measurements since the 1800s have repeatedly verified and quantified the absorptive properties of carbon dioxide that allow it to trap heat in the atmosphere.
- Simple models based on the warming impact of carbon dioxide in the atmosphere match historical changes in temperature.
- Complex climate models, recently acknowledged in the Nobel Prize for Physics, not only indicate a warming of the Earth due to increases in carbon dioxide but also offer details of the areas of greatest warming.

Salawitch et al., 2017, updated with data to the end of 2020, CC BY

When carbon dioxide levels have been high in the past, evidence shows temperatures have also been high. Based on Salawitch et al., 2017, updated with data to the end of 2020, CC BY

- Long-term records from ice cores, tree rings and corals show that when carbon dioxide levels have been high, temperatures have also been high.
- Our neighboring planets also offer evidence. Venus’ atmosphere is thick with carbon dioxide, and it is the hottest planet in our solar system as a result, even though Mercury is closer to the sun.

Chart 4: Temperatures are increasing on every single continent

The rising temperatures are evident in records from every continent and over the oceans.

The temperatures aren’t rising at the same rate everywhere, however. A variety of factors affect local temperatures, including land use that influences how much solar energy is absorbed or reflected, local heating sources like urban heat islands, and pollution.

The Arctic, for example, is warming about three times faster than the global average in part because as the planet warms, snow and ice melt makes the surface more likely to absorb, rather than reflect, the sun’s radiation. Snow cover and sea ice recede even more rapidly as a result.

NOAA Global Monitoring Lab

Chart 5: Rising temperatures = rising oceans

Earth’s climate system is interconnected and complex, and even small temperature changes can have large impacts – for instance, with snow cover and sea levels.

Changes are already happening. Studies show that rising temperatures are already affecting precipitation, glaciers, weather patterns, tropical cyclone activity and severe storms. A number of studies show that the increases in frequency, severity and duration of heatwaves, for example, affect ecosystems, human lives, commerce and agriculture.

Historical records of ocean water levels have shown mostly consistent increases over the past 150 years as glacier ice melts and rising temperatures expand ocean water, with some local deviations due to sinking or rising land.

Permanent Service for Mean Sea Level

Chart 6: If we don’t act, temperatures will keep increasing. So will rainfall

While extreme events are often due to complex sets of causes, some are exacerbated by climate change. Just as coastal flooding can be made worse by rising ocean levels, heat waves are more damaging with higher baseline temperatures.

Climate scientists work hard to estimate future changes as a result of increased carbon dioxide and other expected changes, such as world population. It’s clear that temperatures will increase and precipitation will change. The exact magnitude of change depends on many interacting factors.

Based on SSP3-7.0, a high-emissions scenario. Claudia Tebaldi, et al., 2021

But there are a few reasons for hope

On a hopeful note, scientific research is improving our understanding of climate and the complex Earth system, identifying the most vulnerable areas and guiding efforts to reduce the drivers of climate change. Work on renewable energy and alternative energy sources, as well as ways to capture carbon from industries or from the air, are producing more options for a better-prepared society.

At the same time, people are learning about how they can reduce their own impact, with the growing understanding that a globally coordinated effort is required to have a significant impact. Electric vehicles, as well as solar and wind power, are growing at previously unthinkable rates. More people are showing a willingness to adopt new strategies to use energy more efficiently, consume more sustainably and choose renewable energy.

Scientists increasingly recognize that shifting away from fossil fuels has additional benefits, including improved air quality for human health and ecosystems.

Are we on track to limit global warming to only 1.5 degrees Celsius? The Climate Action Tracker explains the good news and the bad news for the planet:

…

ABOUT THE AUTHOR

Betsy Weatherhead PhD is an atmospheric scientist who has received a number of awards for her scientific work on weather, climate, stratospheric ozone, UV radiation and unmanned aircraft. She is proud to share a number of awards, including the 2007 Nobel Peace Prize as a member of the Intergovernmental Panel on Climate Change for her contributions on understanding the Arctic climate. She has led a number of successful groups to develop programs and increase scientific activity in a number of areas (Arctic research, unmanned aircraft, renewable energy and weather forecasting). She has also brought together leaders from academia, public sector and private sector to identify a path for the U.S. to become significantly better at weather forecasting. She previously worked in the federal government and at Jupiter Intelligence, a company that advises on managing climate change risks. Currently she is working with the international community to understand trends in tropospheric ozone around the globe.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

VultLab

Today, over 1.5 billion children are unable to go to school. Coronavirus’ impact goes beyond the health and economic crisis; it is also jeopardizing the education of students around the world.

Teachers are scrambling to offer students lessons online and parents are desperate for activities that will keep their kids engaged and connected to the outside world.

In response to this crisis, an unprecedented coalition of over fifty environmental and education experts are collaborating to launch The Earth School: 30 adventures for learners of all ages to discover, celebrate, and connect to nature. This global team came together under the guidance and support of TED-Ed and UNEP to design lessons for students of all levels and host Earth School at a time when it matters the most.

These experts have been supported by over 30 organizations including National Geographic, WWF, and the BBC who have offered top caliber videos, articles, and interactive resources that will be shared around the world. The initiative launches on Earth Day on April 22 and will conclude on World Environment Day on June 5. Earth School is comprised of daily adventures, or Quests, each organized around the theme: “The Nature of…” While the initiative is hosted online, the Quests are very much designed to encourage young people to connect with nature and their environment.

Covering real world concepts like the t-shirts we wear, the water we drink, the trees in our forests or the food on our plates, each Quest will consist of a discovery video and fun quiz combined with a series of interactive resources – including additional content to watch, read, teach, do, and share, with age-adjusted exercises built into each lesson.

The team behind Earth School is thrilled that it can help solve three major problems right now:

First, there are so many great environmental resources online that future environment experts don’t know where to begin. Earth School aggregates a wide span of lessons from trusted sources under a single platform. With these lessons, learners of all ages will be able to explore how to live greener and cleaner lives individually and in their communities.

Secondly, young people (in fact, all people!) are stuck inside, more disconnected from nature than ever before. Earth School encourages young people to understand how nature and our ecosystems provide the foundations for a healthy planet, and healthy people. We aim to inspire the awe and wonder of nature in Earth School students and help them finish the program with a firm grasp of how deeply intertwined we are with the planet.

And finally, the team at Earth School aims to help the parents of students around the world, many of whom are taking on their children’s education for the first time. Locating quality lessons and activities online is no easy task; we hope to support them in this unfamiliar moment of global pause and provide the spark of inspiration that will connect young people to nature.

At the Butte County Library in Chico, California, there is a seed section. This is the Chico Seed Lending Library (CSLL), a collection of seeds donated from gardens and farms around the region. At CSLL, advanced and burgeoning gardeners can borrow the means to grow everything from muskmelon to sweet peppers, and learn the traditional art of seed-saving in order to return seeds to the library for other growers.

The library was started after seed-savers Sherri Scott and Stephanie Ladwig-Cooper started to see big crowds at their annual Seed Swap event — and more of their neighbors growing their own food. At Seed Swap events, gardeners bring and exchange seeds saved from that year’s growing season, and over the years, attendance at the Chico Seed Swap exploded, Scott says at TEDxChicoSalon.

“Each year, we [saw] more and more people bringing seeds that they saved back to share with their neighbors,” she says. “But we wanted greater access to seeds for the community and we wanted more education on how to correctly save seeds.” So Scott and Ladwig-Cooper reached out to their local library to seek if they could set up a year-round resource for seed-savers — and a permanent seed collection open to the public. The librarian there was excited — so they launched CSLL.

The seed library is designed to preserve the best of local seeds, Scott says, those from plants that are the “tastiest,” “best-growing” and “resilient,” — those that thrive in the Chico ecosystem, Scott says. She hopes that it will also aid in protecting rare plants, the fruits and vegetables that don’t show up on supermarket shelves.

One of these plants is the Bidwell Casaba melon, a melon closely connected to Chico’s history, as it was developed by Chico resident and Califorina congressman John Bidwell in the early 19th century.

The Bidwell Casaba is one of the several local melon types protected by seed-savers who grew the plant despite its lack of commercial appeal. “The stores won’t carry it because it’s soft; it bruises easily; it’s not easily transported and it’s not easily marketed,” Scott says. “It almost went extinct, but luckily some seed historians and melon enthusiasts rediscovered it.”

Chico Seed Lending Library invites locals to “adopt a crop” to keep regional fruits and vegetables alive, and provide seeds for their neighbors. “Community seed projects are the missing link we need to [sustain] our local food system,” Scott says. “If you don’t have a seed swap, seed banks or seed libraries in your community, it’s really easy to start them.”

To find out more about seed libraries, watch Scott’s TEDx talk. To find out more about seed science, watch this TED-Ed Lesson. 

Art credit: TED-Ed. Author bio: Hailey Reissman writes for TEDx Innovations Blog.

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